Method of making hydrobromic acid



1937. e. F. DRESSEL ET AL 2,070,263

METHOD OF MAKING HYDROBROMIC ACID Filed Oct. 30, 1933 Aeac fion Chamber Adsorber Wafer (a/umn fcrabber florner Kaponjer INVENTOR G'ragfar) f: 0/6558/ BY O/fo 6? 20.55

TTORNEY Patented Feb. 9, 1937 UNITED STATES PATENT OFFICE 2,070,263 METHOD OF MAKING HYDROBROMIC Aom Grayton F. Dressel and Otto 0. Ross, Midland,

Mich, assignors to The Dow Chemical Company, Midland, Mich., a corporation of Michigan Application October 30, 1933, Serial No. 695,743

4 Claims. (01. 23-156) This invention relates to methods of making bath in tank 2. A vertical tube 1 of silica or hydrobromic acid wherein hydrogen and bromine heat resistant glass leads from the top of vaare reacted directly with each other. porizer I and connects the latter with a tubular Various methods have hitherto been used to efreaction chamber 8, likewise preferably made "5 fect the aforesaid reaction. For instance, of. heat-resistant glass. Tube 1 terminates at its 5 bromine vapor and hydrogen may be reacted by upper end in a burner tip 9, just below which in mixing the same in approximately combining the tube is located a small body In of granular proportions, and causing them to burn at a suitporous material, e. g. charcoal. A perforated ably elevated temperature. Another method. cap I l of porcelain, carbon or other heat and corconsists in reacting in vapor phase at a lower rosion resistant material is placed over burner 10 temperature in the presence of a porous catalyst, tip 9, but spaced therefrom, being supported on such as activated charcoal, silica gel, or the like. a shoulder in the lower part of reaction cham- There are some practical disadvantages connected ber 8. Just above the lower end of chamber 8 with both of these procedures which make them is an enlarged section l2 into which the burner unsatisfactory for a commercial process. In the 9 and cap H extend. Through the sides of en 15 first mentioned method it has been found praclargement 12 are inserted two adjustable ignitically impossible to produce a water-white hy tion electrodes l3, connected with a source of drobromic acid solution when the reaction prodcurrent of suitable voltage. not is absorbed in water. This is apparently due The upper end of chamber 8 is connected by a to the existence of free bromine in the product, U tube l4 with a column [5 which contains a 20 which Oc u s e en W an BXCeSS y n body I6 of granular porous adsorbent material, is employed in the reaction and indicates that the such as active charcoal, pumice, silica gel, or reaction does not go entirely to completion, at similar metallic oxide gels. Means is provided least not within the time interval during which for heating the column, for instance an electric the gases traverse the combustion zone. Theoresistance element II. From the bottom of colretically this condition could be remedied by eX- umn l5 a tube 18 connects with the base of a tending the length of the combustion zone sufscrubber column IQ of usual form filled with a ficiently, but this has not been found practical body of packing material, and surrounded by a in apparatus adapted for Commercial Operation Water jacket. A water inlet 20 and vent 2!, are In the aforementioned Catalytic methfid it has provided at the top of scrubber l9, and a trapped 30 been found possible to avoid the presence of free outlet 22 at the bottom, the latter containing bromine in the product, but the rate of reaction a hydrometer well, as shown. is reduced to but a fraction of that of the com- In the operation of the foregoing apparatus a bustion method, and the output from an appabody of liqid bromine is maintained in vaporizer ratus of given size is reduced excessively. l, through which hydrogen is bubbled, thereby 35 We have now devised an improved method for vaporizing bromine and producing a gaseous mixcarrying out the reaction whereby a water-white ture of hydrogen and bromine. The temperature acid solution can be produced continuously at of the vaporizer is held by means of the water bath a rate equal to that obtained in the aforesaid at the proper point in relation to the vapor tencombustion method. The improved method consion of bromine and rate of flow of hydrogen intro- 40 stituting our invention is fuly set forth in the duced, so that a gas-vapor mixture is produced following description which is to be read with in which the volume of bromine is nearly equal reference to the annexed drawing. to that of hydrogen. In practice at the rate of In said drawing: gas flow required to feed the burner, the tempera- The single figure shows diagrammatically a ture of the vaporizer is held between 37 and 42 45 form of apparatus adapted for carrying out the 0., e. about Whereat the miXtllre 0 method of the invention. tains a small excess, e. g. about 10 per cent by Referring to the drawing, a bromine vaporizer volume, o y m The bromine-hydrogen and gas mixing chamber I, made of a metal remixture pa into burner tube n ich 0 sistant to bromine, e. g. lead, or of ceramic math rou h int rmix is a mp s d y pas a e terial, is placed in a temperature regulating wathrough the body of charcoal In, and emerging ter bath in a tank 2. Inlet pipes 3 and 4 serve from the burner p 9 is ignited y 5% p k b to introduce bromine and hydrogen, respect tween electrodes 13. After ignition the reaction ly, into vaporizer I, while a water 1 t 5 d maintains itself and continues as long as the 5 overflow pipe 6 is provided to control the water P p proportions of bromine and y e are 5 maintained. A considerable excess of hydrogen in the mixture will not materially affect the continuance of the reaction, but an excess of bromine is to be avoided, since even a slight excess thereof will extinguish the flame and hence interrupt the reaction. In case the flame should go out for this or any other reason, the gases may be reignited, as in the first place, by means of the spark electrodes. These electrodes are made adjustable, and can be drawn back when not in use. When cap it is made of a conducting material such as carbon, the spark can be drawn between the electrodes and the cap. 7

The rate of introduction of hydrogen gas into the vaporizer i is regulated so as to maintain the temperature in the combustion zone between about 600 and 850 C. We have found that the perforated cap i i over the burner tip 9, by-becoming heated to incandescence, assists the smooth and even burning of the gases. The reaction gases traverse the chamber 8 in which a considerable cooling takes place by radiation, and pass thence into adsorber column l where they are brought into intimate contact with the active charcoal or other adsorbent porous contact material therein, Such charcoal adsorbs unreacted bromine and hydrogen in the gases and holds the gases until they react to form hydrogen bromide. The body of adsorbent material should be heated to an elevated temperature to carry out the reaction of hydrogen and bromine therein. In practice, a temperature between about 150 and 200 C. is suitable, although higher temperatures may be used.

The completely reacted gases, containing no free bromine, are conducted into the base of scrubber 29, wherein they are absorbed in water. By suitably regulating the volume of water admitted at inlet 28 in proportion to the volume of hydrogen bromide in the reaction gases an aqueous hydrobromic acid solution of any strength up to complete saturation may be readily obtained. The temperature of the liquid within the scrubbing column may be controlled by passing cooling water through the water jacket. The strength of the efiluent acid at outlet 22 may be continuously determined by means of the hydrometer as shown. In ordinary operation a strong solution of approximately 48 per cent HBr content is prepared. From outlet pipe 22 the aqueous acid is conducted away for filling into containers.

We have attempted to operate the above described apparatus while dispensing with a charge of adsorbent material in column IE, but have not succeeded in this way in preparing water-white hydr-obromic acid. Inasmuch as a water-white acid is required for most commercial purposes, the purity of the product made is of first importance, hence we have found it necessary, in employing the combustion method of reacting bromine and hydrogen, to combine therewith the step of passing the gases through a body of adsorbent material in order to obtain a suificiently pure product.

A particular advantage of our improved method is the relatively high capacity of the apparatus as compared with the prior art method in which the reaction of bromine and hydrogen is carried out entirely within a body of contact material. In our experience with the commercial operation of such last-mentioned method, employing activated charcoal for the contact material, the highest yield of hydrogen bromide, figured as 100 per cent HBr, obtained was approximately 6 pounds per 24 hours per square inch cross section of the reaction chamber. On the other hand, with the method and apparatus of the present invention, employing a body of active charcoal of the same depth as before, we are enabled to produce from 35 to 40 pounds of 100 per cent HBr per 24 hours per square inch cross section of the adsorber, as substantially pure water-white acid solution. Another advantage is that the accidental introduc tion of excess bromine, or the extinguishment of the flame for any cause, will not result in the carrying forward of unreacted bromine to contaminate the hydrobromic acid solution product. Such excess bromine is adsorbed on and held by the active charcoal or other adsorbent employed, while the hydrogen bromide passes through. Subsequently such adsorbed bromine is converted in situ to hydrogen bromide by reaction with hydrogen, when the presence of a sufiicient excess thereof in the reaction gases is re-established. The method, then, is adapted for the uninterrupted production of pure water-white hydrobromic acid solution regardless of irregularities in supplying the proper proportions of hydrogen and bromine to the burner, or other disturbances which interfere with complete reaction of the bromine.

Other modes of applying the principle of our invention may be employed instead of the one explained, change being made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

We therefore particularly point out and distinctly claim as our invention:-

1. The method of making water-white hydrobromic acid solution which comprises passing hydrogen through a body of liquid bromine maintained at a temperature between 37 and 42 C. to form an approximately equimolecular mixture of bromine vapor and hydrogen, burning the mixture, while causing the flame to impinge upon a surface of heat resistant material maintained at incandescence by the heat of the flame, partially cooling the combustion gases, passing the latter through a body of active charcoal maintained at a temperature between about 150 and about 200 C., and absorbing the purified hydrogen bromide gas in water.

2. The method of making water-white hydrobromic acid solution which comprises passing hydrogen through a body of liquid bromine maintained at a temperature between 37 and 42 C. to form an approximately equimolecular mixture of bromine vapor and hydrogen, thoroughly intermixing the vapors and gases by passing through a body of porous granular material, burning the mixture, while causing the flame to impinge upon a surface of heat resistant material maintained at incandescence by the heat of the flame, partially cooling the combustion gases, passing the latter through a body of active charcoal maintained at a temperature between about 150 and about 200 C., and absorbing the purifled hydrogen bromide gas in water.

3. The method of making water-white hydrobromic acid solution which comprises passing hydrogen through a body of liquid bromine maintained at a temperature between 37 and 42 C. to form an approximately equimolecular mixture of bromine vapor and hydrogen, thoroughly intermixing the vapors and gases by passing through a body of porous granular material, burning the mixture, while causing the flame to impinge upon a surface 01' heat resistant material maintained at incandescence by the heat of the flame, regulating the rate of supply of hydrogen so that the temperature in the combustion space is maintained between about 600 and about 850 C., partially cooling the combustion gases, passing the latter through a body of active charcoal maintained at a temperature between about 150 and about 200 C., and absorbing the purified hydrogen bromide gas in water.

4. The method of making water-white hydrobromic acid solution which comprises passing hydrogen through a body of liquid bromine maintained at a temperature between 37 and 42 C. to form a mixture of bromine vapor and hydrogen containing a slight excess of hydrogen, burning the mixture, while causing the flame to impinge upon a surface of heat resistance material maintained at incandescence by the heat of the flame, partially cooling the combustion gases, passing the latter through a heated body of adsorbent porous contact material, and absorbing the purified hydrogen bromide gas in water.

GRAYTON F. DRESSEL. OTTO C. ROSS. 

